For ease of dosing, rennet is most frequently marketed in solution form. In general, however, rennet solutions are not as stable as rennet powder, in regard to rennet activity, especially when subjected to elevated storage temperatures. As might be expected under these circumstances, addition of stabilizing agents to the rennet solution in order to improve the stability has been suggested to the art. Sorbitol has been commercially used for stabilizing agent, usually in an amount of around 50% (w/w) calculated on the solution.
Most, but not all, of any stabilizing agent added to a rennet solution will be taken up by the whey phase. However, since some small part will be taken up by the curd phase, some of the stabilizing agent will be present ultimately in the cheese. For reason that it is a foreign material, the presence of sorbitol in the cheese is most undesirable and, as a matter of fact, sorbitol is not approved in some countries for stabilization of rennet. Further, sorbitol is a relatively expensive material, and because around 50% of sorbitol has to be added in order to obtain a reasonable stabilization, the price of the stabilized rennet solution is considerably higher than that of the unstabilized rennet solution.
Thus, a need exists for a stabilized solution of rennet, wherein the stabilizing agent would not be considered a foreign substance, and wherein inclusion of the stabilizing agent does not add very much to the price of the rennet solution.
The present invention is based upon discovery that small amounts of methionine exhibits a strongly stabilizing effect on the enzymatic activity of a rennet solution.